1. Scope of Invention
This invention relates generally to a tiltable truck bed of a dump truck, and more particularly to a tailgate apparatus for automatically opening and closing the tailgate in an amount directly responsive to, and positively controlled by, the tilted angle of the truck bed.
2. Prior Art
A tailgate of a dump truck having a tiltable truck bed for emptying debris piled into the truck bed is typically attached to the upper rear ends of the side walls by a pivotal connection with the upper corners of the tailgate. When dumping a load of debris, the lower or bottom edge of the tailgate is released from a locked position by an operator and allowed to pivot outwardly from the side walls and the bottom of the truck bed as the truck bed is tilted upwardly.
To dump a load of debris, however, these typical dump trucks require that the operator physically unlock the tailgate before the truck bed is raised. Likewise, the operator must then resecure the otherwise freely pivotable tailgate before leaving the dump sight.
An improved tailgate apparatus is disclosed in U.S. Pat. No. 4,068,892 invented by Welch disclosing a tailgate apparatus which does apparently by gravity automatically raise and lower without the use of a power source and without the need for a locking device which prevents the tailgate from opening while debris is being transported within the truck bed.
However, all of the prior art devices and apparatus known to applicant, including the above Welch invention, do not provide for a positive means for lifting the tailgate above the plane of the upper margins of the side walls to readily facilitate dumping debris contained within the truck bed and which may be piled higher than the side walls. Typically, debris from tree cuttings, paper collection and other debris of a less dense nature can easily be piled above the side walls of the dump truck and remain there secured whether covered or uncovered, while being transported. However, when the prior art dump truck bed is tilted for dumping, the debris piled high above the side walls will jamb and become wedged on the tailgate or tilting mechanism to prevent effective dumping. In such circumstances, the operator must again move to the rear of the truck bed and physically dislodge the jammed debris to effect complete dumping thereof.
An unpatented rear end dump truck is currently being manufactured by Workman and Sons, Inc. of Prineville, Oreg. which somewhat addresses this problem of dumping debris piled higher than the side walls of the truck bed. However, the Workmen-type and dump trucks address this issue by simply adding structure above the side walls near the ends thereof so that the pivotal point of the tailgate is substantially raised above the upper margins of the side walls.
Applicant is aware of several other patented prior art dump truck arrangements, none of which are as similar to the present invention as those prior art devices above described. These additional patented inventions are disclosed in the following U.S. patents:
U.S. Pat. No. 3,890,006 to Stockwell PA1 U.S. Pat. No. 4,371,208 to Stricker PA1 U.S. Pat. No. 4,699,428 to Vick PA1 U.S. Pat. No. 4,059,307 to Neufeldt PA1 U.S. Pat. No. 3,230,014 to Mutti, et al. PA1 U.S. Pat. No. 4,343,511 to Rowan et al. PA1 U.S. Pat. No. 4,659,147 to Smiltneek PA1 U.S. Pat. No. 5,030,053 to Wickizer PA1 U.S. Pat. No. 5,100,279 to Bjerk PA1 U.S. Pat. No. 4,269,039 to Baker
The present invention does provide a tailgate apparatus for a dump truck which arcuately moves the tailgate in positive fashion in direct response to the angular tilting of the truck bed. The tailgate, when substantially fully opened by the truck bed being fully tilted for dumping, is positioned substantially above a plane defined by the upper margins of the side walls so that debris piled higher than the side walls will be easily dumped without the need for manual operator assistance. Further, the tailgate will be securely retained in the closed position without the need for operator locking, although same is preferred for secondary or supplemental insurance of tailgate lockage.